WinRho: Rh immune globulin prepared by ion exchange for intravenous use.

An Rh immune globulin [Rh IgG] for intravenous use, WinRho, has been prepared by the Winnipeg Rh Institute by a modification of the ion-exchange column method of Hoppe and colleagues. When administered to Rh-negative male and nonpregnant female volunteers WinRho was found to be nonpyrogenic, nontoxic, safe and protective against Rh alloimmunization. In a clinical trial with 240 microgram given at about 28 weeks'' gestation and 120 microgram given after delivery to Rh-negative women at risk of Rh immunization WinRho was effective in preventing Rh immunization. Of the 870 women carrying Rh-positive fetuses who were treated with WinRho during pregnancy and were not tested several months after delivery 14 would have shown evidence of Rh immunization by the time of delivery if WinRho had been ineffective; none showed such evidence. Of the 1122 women carrying Rh-positive fetuses who were retested 4 to 6 months after delivery 83 would have shown evidence of Rh immunization at that time if WinRho had been ineffective; only 1 showed such evidence. The efficiency of yield of anti-D with the modified method of production, the fct that it can be given intravenously (a route that causes the patient less discomfort and immediately results in high anti-D levels) and the lower levels of contaminating IgA and IgM make WinRho the preparation of choice for preventing Rh immunization.     

Rh isoimmunization during pregnancy: antenatal prophylaxis.

Of 3533 Rh-negative women who began a pregnancy without detectable Rh antibodies, 62 (1.8%) demonstrated evidence of Rh isoimmunization during pregnancy or within 3 days after delivery. All denied transfusions as well as abortions or previous pregnancies not followed by the administration of Rh immune globulin. Rh isoimmunization during pregnancy or within 3 days after delivery, which will not be prevented by the administration of Rh immune globulin after delivery, is the most important cause of residual Rh isoimmunization. A clinical trial of antenatal administration of Rh immune globulin, initially at 34 weeks''s and subsequently at 28 and 34 weeks'' gestation, in 1357 Rh-negative pregnant women who were delivered of Rh-positive babies, was effective in preventing the development of Rh isoimmunization during pregnancy or within 3 days after delivery. Antenatal prophylaxis with Rh immune globulin will be necessary if the incidence of Rh isoimmunization is to be reduced to its lowest possible level. Antenatal prophylaxis at 28 weeks'' gestation is now an insured service in Manitoba.     

Prevention of Rh Hemolytic Disease of the Newborn

Rh_o(D)-Immune Globulin was given to 322 Rh-negative women delivered of ABO-compatible, Rh-positive infants with no apparent failures to suppress Rh sensitization. In contrast, 32 of 305 mothers of a control group made Rh antibody during the six months following delivery. In subsequent pregnancies, 69 women administered RhoGAM had no evidence of isoimmunization after delivery while six of forty mothers of the control study produced anti-Rh. RhoGAM, given within 72 hours of delivery in the amounts employed, was effective for suppression of Rh immunization.     

Antenatal prophylaxis of Rh isoimmunization: 28-weeks'-gestation service program

Two (0.18%) of 1086 Rh-negative primigravidas or multigravidas treated similarly in all previous pregnancies, who were given a single injection of Rh immune globulin (300 μg) at 28 weeks'' gestation and subsequently were delivered of Rh-positive babies, had demonstrable Rh isoimmunization at the time of that injection and must be considered “logistic” failures of antenatal prophylaxis. The remaining 1084 (who were treated again after delivery) had no evidence of Rh isoimmunization at delivery and none of the 512 screened at 6 months after delivery appeared to be immunized. If the 28th-week injection had not been protective, one would have expected 14 of the 1084 to have been demonstrably Rh isoimmunized and evidence of Rh isoimmunization to have persisted in 6 of the 512 observed 6 months after delivery.Six of 719 Rh-negative multigravidas who had not received Rh immune globulin after previous pregnancies or had been treated only after delivery showed evidence of Rh isoimmunization despite a single injection of Rh immune globulin at 28 weeks in a subsequent pregnancy. In three of the six the cause was most likely “sensibilization” due to previous exposure to Rh-positive blood or an untreated Rh-positive pregnancy. in 3 of the remaining 716 (0.42%) there may have been true failure of antenatal Rh prophylaxis administered at the 28th week. One would have expected this figure to be 12 of 716 if antenatal Rh prophylaxis at 28 weeks'' gestation were totally unsuccessful.It is concluded that a single intramuscular injection of Rh immune globulin, 300 μg, is 88% effective in preventing Rh isoimmunization during pregnancy in Rh-negative primigravidas and in multigravidas treated antenatally in all previous pregnancies, and is 75% effective in preventing Rh isoimmunization in Rh-negative multigravidas untreated during previous pregnancies. The majority of failures are due to Rh isoimmunization during pregnancy prior to antenatal prophylaxis at 28 weeks.     

Rh-immunization by Pregnancy: Results of a Survey and Their Relevance to Prophylactic Therapy

A series of Rh-negative primiparae has been studied in order to gain further insight into the process of immunization by pregnancy. The distribution of foetal cell counts in blood samples taken after delivery was determined for 2,029 mothers giving birth to ABO-compatible babies and for 417 mothers with ABO-incompatible babies.A total of 760 mothers were tested for the development of Rh antibodies six months after the delivery of an ABO-compatible Rh-positive baby and 236 were further followed up through a second Rh-positive pregnancy. The incidence of anti-D six months after delivery is estimated to be 8.5%, and there is evidence of a direct relation between the count of foetal cells after delivery and the risk of developing antibodies. A further 8.5% of mothers were estimated to develop anti-D by the end of the second pregnancy, and it is postulated that these individuals had been primed by the first pregnancy. There is some evidence that the larger stimuli of Rh-positive blood in the first pregnancy are more likely to result in overt antibody formation, while the smaller stimuli are more likely to prime, antibodies not being detected until a second stimulus occurs during the second pregnancy.These findings are relevant to the programme for preventing Rh-immunization by injecting anti-D gammaglobulin.     

An error in Rh testing in pregnancy.

Anti-D (anti-Rho) in the blood of two Rh-negative pregnant women was believed to be due to active immunization. In the first case, however, antibodies were no longer detectable 2 weeks later. In the second case they disappeared by the end of 31 weeks. It was discovered that both women had been given immune globulin (human) because of exposure to rubella. The globulin given to the first woman probably contained about 0.1 mug of anti-D per ml; that given to the second probably contained about 0.6 mug of anti-D per ml. Both babies were O Rh-positive. Both women were given Rh immune globulin after delivery. Both have completed a further pregnancy and no anti-D has been found on many tests. In tests carried out in 1971 all samples of immune globulin (human) examined contained anti-D, but usually in inconsequential trace amounts.     

Clinical Evaluation of Rh0(D) Immune Globulin (Human) in Canada

—During 1966, clinical trials were conducted in three Canadian centres to determine the safety and efficacy of Rh₀(D) immune globulin (human) in preventing isoimmunization by the Rh₀(D) antigen in Rh-negative women delivering ABO-compatible Rh-positive infants.The candidates were randomly divided into control and treated groups; the treated mothers received an intramuscular injection of 300 μg. of anti-Rh₀(D) within 72 hours of delivery. Follow-up antibody screening tests were conducted on the sera of all patients six to nine months post partum.Of the 175 control patients, 11 or 6.2% became actively immunized to the Rh antigen, whereas complete protection against maternal Rh immunization was observed in the 191 treated patients.     

Association between Foeto-maternal Bleeding and Hypertension in Pregnancy

A blind prospective survey of foeto-maternal bleeding in 200 primiparous pregnancies was carried out in an investigation of a possible association between foeto-maternal bleeding and hypertension in pregnancy. Evidence of foeto-maternal bleeding was found in 61% of 36 hypertensive pregnancies, and in 51% of 160 normotensive pregnancies, a difference which is not statistically significant.Significant differences between the hypertensive and the normotensive groups were found when foeto-maternal bleeding was related to gestation. In pregnancies that became hypertensive more foetal cells were found in the maternal circulation before week 36 than in normotensive pregnancies. In patients with oedema of the abdominal wall during pregnancy the incidence of foeto-maternal bleeding was significantly increased.These findings seem to explain why pre-eclamptic toxaemia is a significant predisposing factor in women who later develop Rh antibodies. It is recommended that anti-D gammaglobulin should be offered to all Rh-negative women with Rh-positive infants following a hypertensive pregnancy. Consideration should also be given to the question of administering anti-D gammaglobulin during Rh-negative hypertensive pregnancies if this procedure is proved to be both safe to mother and foetus and effective.The results provide contributory evidence that the placental vascular changes in toxaemic pregnancies precede the clinical signs and are not the result of hypertension.     

Prevention of Rh-haemolytic Disease: Results of the Liverpool “Low-risk” Clinical Trial

A clinical trial is reported in which Rh-negative primiparae, just delivered of an Rh-positive ABO-compatible infant and in whom fetal cell counts after delivery suggested less than 0·2 ml of circulating fetal blood, were treated with about 200 μg of anti-D gammaglobulin. Three (0·36%) out of 844 women thus treated developed anti-D in the subsequent six months; this is 10% of the incidence in untreated controls. Three (1·8%) out of 171 treated mothers had anti-D at the end of the second Rh-positive pregnancy, and this is 18% of the incidence in controls.Possible reasons for the occasional failure of the treatment are discussed and the results of this trial are compared with those of a previous trial in which 1,000 μg or more of anti-D was given to a different group of mothers. The combined results of the two trials lead to the conclusion that the passive administration of anti-D gammaglobulin after delivery affords in this population of Rh-negative women a 95% protection rate in the postdelivery period and an 89% protection rate by the end of the subsequent pregnancy.     

Effect of ABO Incompatibility on Pregnancy-Induced Rh Isoimmunization

The protective effect of ABO incompatibility between mother and fetus in respect of pregnancy-induced Rh isoimmunization has been recognized for approximately 20 years. Many have tacitly assumed that this protection was absolute and that when an infant was born with Rh hemolytic disease of the newborn, who was also ABO-incompatible with its mother, there must have been a previous ABO-compatible pregnancy in which the mother was initially sensitized. It has also been assumed that pregnancy-induced Rh isoimmunization could not occur if the father was AB and the mother O. Data are presented to show that both of these assumptions are not universally true. In a detailed study of a large number of families with pregnancy-induced Rh iso-immunization, nine families were found in which sensitization occurred and in which ABO incompatibility was present in every pregnancy. In addition, three families are documented in which pregnancy-induced Rh immunization had occurred and in which the father was AB and the mother O.     

Distribution of blood antigens A, B, and D, in the population of Bogotá (Analysis of 30,000 samples)

As tested by anti-A and anti-B sera, blood drawn from 30,000 inhabitans of Bogotá, Colombia, showed the following phenotype percentages: A — 26.5, B — 8.0, AB — 1.1, and O — 64.4. The allele frequencies were: A — 0.150, B — 0.048, and O — 0.802. In the same samples anti-D (Rh₀) was used: 94.6% of the individuals carried the D antigen. All bloods were typed with fresh commercial sera. No back-typing was performed. Hemolytic disease of the newborn, caused by Rh-Hr isoimmunization, is more frequent (0.40%) in Bogotá than should be expected for a population having only (5.4%) or less “Rh negative” individuals. This paradoxical fact was observed in the analysis of 12,672 deliveries in an obstetrical hospital of Bogotá. A possible explanation could be the multiparity of Colombian women since the possibility of isoimmunization and hemolytic disease increases with each succeeding pregnancy in a given woman. Also it is well established that when Rh-Hr incompatibility is combined with ABO incompatibility, it is less apt to produce disease than when it occurs alone. AO isoimmunization should therefore be less frequent in Bogotá than in populations that have a higher frequency of A individuals. Thus, the women of Bogotá are less “protected” from Rh-Hr immunization by ABO incompatibility.     

Rh immunization in Manitoba: progress in prevention and management.

For two decades the perinatal mortality caused by erythroblastosis has been decreasing in Manitoba. The improved management of Rh-immunized pregnancies has lowered the death rate among affected infants from 10.8% to 3.4%, while the prevention of Rh immunization has reduced its incidence from 9.1 to 2.2 per 1000 total births. In its first 6 years and 8 months Manitoba''s antenatal prophylaxis program, in which immunoglobulin is administered to Rh-negative women at 28 weeks'' gestation, reduced the incidence of Rh immunization during pregnancy by 93%. In combination with post-abortion and postpartum prophylaxis the antenatal treatment has provided a protection rate of 98.6% among primigravidas at risk. Further improvements are expected.     

Demonstration of the activity of a rhesus-positive antigen in the erythrocytes of rhesus-negative donors and an increase in the expression of ABO system antigens after ultraviolet irradiation of the blood

UV irradiation (254 nm) in doses increasing erythrocyte (Er) hemolysis by 5 to 32% was found to stimulate the agglutination activity of ABO and Rhesus (Rh) system antigens. The stimulation effect was the higher the lower the antigen activity before irradiation. In the Rh-negative (Rh-)-Er, irradiation induced the Rh0(D)-like antigen specific activity suggesting that this antigen may be present in the Rh--Er membrane. Expression of Rh0(D)-antigen in Rh--Er, stimulation of its activity in Rh-positive cells, and activation of ABO system antigens may result from photo-chemical destruction of the outer membranous layer of the ER.     

ABO and Rh blood groups in relation to sex ratio, mean number and mortality of sibs.

Data are presented on the sex ratio, mean number and mortality of the sibs of 17,060 schoolchildren, and on the sex ratio and mean number of the sibs of 5,785 blood donors, in relation to the children's and donors' sex and ABO and Rh blood groups. The sex ratio is significantly higher for the sibs of AB + B than for those of A + O schoolboys, and for the sibs of Rh-negative than for those of Rh-positive male blood donors, but in both cases the mean number of sibs is exactly the same for the first-mentioned as for the second-mentioned category.     

Compliance with postpartum Rh isoimmunization prophylaxis in Alberta

A retrospective review of obstetric records for 1979 in two major Calgary hospitals was undertaken to determine the rate of compliance with postpartum Rh isoimmunization prophylaxis in Alberta. The charts of 4528 women ranging in age from 13 to 46 years were reviewed. The prevalence rate of Rh negativity was found to be 16%. Of the 710 Rh-negative women 490 (69%) were eligible to receive Rh immune globulin (RhIG); that is, they had no anti-D antibodies, and the baby/fetus was Rh-positive or Rh-unknown. RhIG had been administered to 93.6% of the eligible women; the compliance rate ranged from 66.7% for obstetric emergencies (i.e., spontaneous abortion, antepartum or early-pregnancy hemorrhage, or ectopic pregnancy) to 98.2% for postpartum diagnoses. In more than half (54.7%) of the women who underwent amniocentesis Rh type was not determined; the implications of this finding are discussed. Although poor compliance with postpartum RhIG administration is not a reason for withholding antepartum administration of RhIG, maximum compliance with the more cost-effective programs should be attained before antepartum programs are fully implemented.     

Segregation distortion in Rh polymorphism

Segregation distortion for the Rh system is reported. Mother-infant pairs (1018 pairs) from maternity service divisions of government hospital and 216 complete families with a total of 692 children, of Visakhapatnam (Andhra Pradesh, South India) were typed for the D-d alleles of Rh system. The segregations analysis made by means of the T matrix method of ITO matrices, assuming Hardy-Weinberg equilibrium, reveals that: Rh-positive mothers produce fewer Rh-negative children with significance and Rh-negative mothers produce more Rh-positive children with less significance than expected in both the mother-child and family studies. This results in a reduction in the d allele from mothers to their children. Known Rh antigenic specificities and reproductive compensation do not explain the observed distortion. Other selectively acting forces probably linked to Rh compatibility system seem to be operating to gain d alleles to maintain Rh polymorphism.     

BLOOD TRANSFUSIONS AND THE Rh FACTOR

When Rh-negative persons are given transfusions of Rh-positive blood, more than 50 per cent are sensitized to the Rh₀ factor. Such sensitization of female children may be the cause of hemolytic disease in their offspring many years later, while severe hemolytic reactions may follow a second transfusion of Rh-positive blood in either sex.The gross hemolysis of transfused blood may be entirely asymptomatic, however. In one case a pint of blood was completely hemolyzed within two hours without producing symptoms. The only signs were hemoglobinuria, low grade jaundice, urobilinogenuria and a rising Rh antibody titer. The patient had previously been sensitized by a single pint of Rh-positive blood.The dangers of Rh sensitization can be avoided by routine Rh typing of all prospective recipients of transfusion, whether male or female, and by giving only Rh-negative blood to those who are Rh-negative.     

The experience and effectiveness of the Nova Scotia Rh program, 1964-84.

A program to reduce the incidence of erythroblastosis fetalis was started in Nova Scotia in 1964. Up to the end of 1984, 120 fetuses received 247 intrauterine transfusions. The survival rate was 45.6% in the first 10 years of the program and 66.7% in the next 11 years. For fetuses at or over 26 weeks'' gestation the figures were 51.5% and 73.7% respectively. Postpartum prevention was started in 1968, with administration of Rh immune globulin (RhIG) to Rh-negative unimmunized women within 72 hours after the birth of an Rh-positive infant. Antepartum prevention, started in 1979, consisted of administration of RhIG at 28 weeks'' gestation to Rh-negative unimmunized women. The effectiveness of the prevention program was evaluated by enumerating the known cases of Rh(D) alloimmunization in the province from 1982 to 1984: 55 cases were identified, a rate of 1.5 per 1000 births instead of the expected rate of about 10 per 1000.     

Reduced severity of Rh-haemolytic disease after anti-D immunoglobulin.

A total of 2459 Rh-negative women who received anti-D immunoglobulin after a Rh-positive pregnancy were followed up in at least one subsequent pregnancy. There was a failure of protection rate of 1-6%. Follow-up of 53 subsequent infants of mother in whom protection had failed showed that the infants were less severely affected than would have been expected. This was confirmed by a comparative statistical analysis of the present series and a series of first affected cases before anti-D immunoglobulin was available, using the antibody titre during pregnancy and the haemoglobin levels at delivery.     

Prevention of Rh-haemolytic Disease: Final Results of the “High-risk” Clinical Trial: A COMBINED STUDY FROM CENTRES IN ENGLAND AND BALTIMORE

The final results are reported of a trial of about 1,000 μg of anti-D gammaglobulin given intramuscularly to a selected high-risk group of Rh-negative primiparae just delivered of an ABO-compatible Rh-positive baby, the aim being to prevent them becoming immunized to Rh. Six months after delivery only 1 out of 173 treated mothers had been immunized as against 38 out of 176 controls. The crucial test of the prophylactic therapy depends on the presence or otherwise of anti-D at the end of a second Rh-positive pregnancy. Of 86 treated mothers two had antibodies at this time compared with 20 out of 65 controls.The results show a high degree of protection in this group of mothers.